large amount of lilies

I have a small 55 gal pond in my yard. I have gold fish in the pond and was given lilies to put in the pond for the fish. My question is how many lilies should be in a pond this size? Over 80% of the water is covered with lilies, and the fish never see much more than 20% of daylight. I need your advice. Thank you, aleenix1@comcast.net